Over the many years I've been playing tennis I have had bouts with elbow and wrist problems, but never a shoulder. In the last few days I have having some pain;tenderness in the front of the shoulder, it's not horrible pain, and so far doesn't really hurt much when I play. Pain is worst if I extend arm out to the side and then pull arm back. That is actually pretty painful and tender. Any ideas? Is this rotatar cuff or something else?